Stromal Low Temperature Compartment Derived from the Inner Membrane of the Chloroplast Envelope

Morré, D. James; Selldén, G.; Sundqvist, Christer; Sandelius, Anna Stina

doi:10.1104/pp.97.4.1558

Cited by 100 publications

(79 citation statements)

References 26 publications

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“…All of these proteins could tentatively be considered substrates of SEC2. Even the thylakoid translocase components needed to be seriously considered, because they are multispanning membrane proteins that appear not to be localized by the known thylakoid pathways (Kroll et al, 2001;Asakura et al, 2004;Martin et al, 2009) and because inner envelope invaginations are thought to produce thylakoids via membrane flow during chloroplast development (Hoober et al, 1991;Morré et al, 1991;Kroll et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

Identification of Putative Substrates of SEC2, a Chloroplast Inner Envelope Translocase

Martin

Aldama

et al. 2017

Plant Physiol.

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Most chloroplast proteins are synthesized in the cytosol and imported into chloroplasts. Many imported proteins are further targeted to the thylakoid membrane and lumen by the SEC1, TAT, or SRP/ALB3 translocases. Others are targeted to the inner chloroplast envelope membrane by undescribed translocases. Recently, a second SEC system (SEC2) consisting of SCY2, SECE2, and SECA2 was found in the chloroplast envelope. Null mutants of SCY2 in Arabidopsis (Arabidopsis thaliana) exhibit a severe embryo-lethal phenotype. To investigate the function of the SEC2 system in plants, we used inducible RNA interference to knock down SCY2 in Arabidopsis. Seedlings cultured with inducer were chlorotic with aberrant chloroplasts and undeveloped thylakoids, indicating an essential role for SCY2 in chloroplast biogenesis beyond embryo development. In SCY2 down-regulated seedlings, several thylakoid membrane proteins, including SCY1, ALB3, and TATC, and inner envelope membrane proteins, including TIC40, TIC110, and FTSH12, were reduced substantially, suggesting that they may be SEC2 substrates. Additional insight was achieved by the in vitro reconstitution of protein integration into chloroplast membranes. The results show that SCY1 and ALB3 target directly to the thylakoid membrane and are likely independent of SEC2. FTSH12 was integrated into the envelope membrane in a coupled import-integration reaction that was impaired by the SECA inhibitor sodium azide. The stromal intermediate of TIC40 integrated into the envelope in a reaction that was largely inhibited when antibodies against epitope-tagged SCY2 or SECE2 were applied. These data demonstrate that the SEC2 translocase likely integrates a subset of inner envelope membrane proteins, such as FTSH12 and TIC40.

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Section: Discussionmentioning

confidence: 99%

Identification of Putative Substrates of SEC2, a Chloroplast Inner Envelope Translocase

Martin

Aldama

et al. 2017

Plant Physiol.

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“…Our knowledge about this lipid transfer mechanism is very imprecise but there are some indications supporting vesicular trafficking. Vesicle budding from the plastid envelope inner membrane was observed by electronic microscopy [68,69]. An Arabidopsis thaliana thylakoid formation 1 (Thf 1) gene product was shown to control a step required for the organization of vesicles derived from the envelope inner membrane into mature thylakoid stacks [70].…”

Section: Transfer From the Plastid Envelope To The Thylakoidsmentioning

confidence: 99%

Glycerolipid transfer for the building of membranes in plant cells

Jouhet

Maréchal

Block

2007

Progress in Lipid Research

134

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“…If cpTatC is initially inserted in the inner envelope membrane, this would necessitate envelope-to-thylakoid relocation by a membrane-flow transport system. Evidence that a system of this kind exists in chloroplasts has been presented by other investigators (Hoober et al, 1991;Morré et al, 1991;Westphal et al, 2001). Sodium azide, which has been shown to inhibit SecA function, was previously used to identify substrates of the SECA1/SCY1 system in pea chloroplasts (Yuan et al, 1994) and in principle could be used to verify usage of the SECA2/SCY2 system.…”

Section: Role Of Secementioning

confidence: 99%

Plastids Contain a Second Sec Translocase System with Essential Functions

et al. 2010

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Proteins that are synthesized on cytoplasmic ribosomes but function within plastids must be imported and then targeted to one of six plastid locations. Although multiple systems that target proteins to the thylakoid membranes or thylakoid lumen have been identified, a system that can direct the integration of inner envelope membrane proteins from the stroma has not been previously described. Genetics and localization studies were used to show that plastids contain two different Sec systems with distinct functions. Loss-of-function mutations in components of the previously described thylakoid-localized Sec system, designated as SCY1 (At2g18710), SECA1 (At4g01800), and SECE1 (At4g14870) in Arabidopsis (Arabidopsis thaliana), result in albino seedlings and sucrose-dependent heterotrophic growth. Loss-of-function mutations in components of the second Sec system, designated as SCY2 (At2g31530) and SECA2 (At1g21650) in Arabidopsis, result in arrest at the globular stage and embryo lethality. Promoter-swap experiments provided evidence that SCY1 and SCY2 are functionally nonredundant and perform different roles in the cell. Finally, chloroplast import and fractionation assays and immunogold localization of SCY2-green fluorescent protein fusion proteins in root tissues indicated that SCY2 is part of an envelope-localized Sec system. Our data suggest that SCY2 and SECA2 function in Sec-mediated integration and translocation processes at the inner envelope membrane.

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Stromal Low Temperature Compartment Derived from the Inner Membrane of the Chloroplast Envelope

Cited by 100 publications

References 26 publications

Identification of Putative Substrates of SEC2, a Chloroplast Inner Envelope Translocase

Identification of Putative Substrates of SEC2, a Chloroplast Inner Envelope Translocase

Glycerolipid transfer for the building of membranes in plant cells

Plastids Contain a Second Sec Translocase System with Essential Functions

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